Classic Streamliners - TRAIN​CYCLOPEDIA

WP No. 2001, the first production GP20, leads a special train in 2009. Note the high nose.  Photo by Drew Jacksich.

By Drew Jacksich from San Jose, CA, The Republic of California (187xRP) [CC BY 2.0 (], via Wikimedia Commons

EMD GP20 Diesel-Electric Locomotive
The EMD GP20 is a 4-axle (B-B) diesel-electric locomotive built by General Motors' Electro-Motive Division between November 1959 and April 1962. Power was provided by an EMD 567D2 16-cylinder turbocharged engine which generated 2,000 horsepower (1,500 kW). EMD was initially hesitant to turbocharge their 567-series diesel engine, but was spurred on to do so following successful tests made by Union Pacific in the form of UP's experimental Omaha GP20units. 260 examples of EMD's production locomotive model (with the EMD turbocharger) were built for American railroads.

The GP20 was the second EMD production locomotive to be built with an EMD turbocharged diesel engine, sixteen months after the six-axle (C-C) model SD24. Power output of the turbocharged SD24 was 33 percent higher than the 1,800 hp (1,340 kW) of the concurrent Roots blower-equipped SD18s with the same engine displacement, 400 hp (298 kW) per axle, but the power output of the turbocharged GP20 was only 11 percent higher than the 1,800 hp (1,340 kW) of the concurrent Roots blower-equipped GP18s with the same engine displacement 500 hp (373 kW) per axle, due to the limitations of the traction motors then available (this limitation was eliminated in the 40-Series). Nevertheless, the turbocharged GP20 provided full rated power at all altitudes, which the Roots-blown GP18 could not provide.

EMD-type Turbo-Compressor (Turbocharger)
The turbocharger was the then-new EMD mechanically assisted turbo-compressor. During engine startup, and at lower power levels, during which there is not sufficient exhaust heat energy to drive the turbine fast enough for the compressor to supply the air necessary for combustion, the engine drives the compressor through a gear train and an overrunning clutch. At higher power levels, the overrunning clutch is disengaged, and the turbo-compressor operates as a true turbocharger. It is possible for the turbo-compressor to revert to compressor mode momentarily during commands for large increases in engine power. Turbocharging provides higher horsepower and good running characteristics at all altitudes. Turbocharging also improves fuel consumption and reduces emissions.

Previous Union Pacific experiments with turbocharging had utilized multiple Elliot or Garrett AiResearch turbochargers feeding the usual pair of Roots blowers. EMD's mechanically assisted turbocharger eliminated the need for the pair of Roots blowers and also integrated the turbocharging function from two (Elliot) or four (AiResearch) smaller add-on turbochargers into one much larger, turbo-compressor (turbocharger) with intercooling.

The introduction of the EMD-type turbocharger was successful and all subsequent GP series were offered with this turbocharger, although not all models within a series were offered with turbocharging (e.g., the 38 sub-models within the 40 Series were Roots-blown).

Units built for the Great Northern Railway were equipped with high short-hoods and were set up to run long-hood forward with a single control stand. Western Pacific received ten GP20s with high short-hoods and dual control stands, thereby facilitating running both long-hood forward and short-hood forward.

While the EMD SD24 with six axles was producing 2,400 horsepower (1,800 kW) with an engine of the same displacement  (400 horsepower (300 kW) per axle), the four axle GP20 was limited to 2,000 horsepower (1,500 kW) (500 horsepower (370 kW) per axle) by the capabilities of the traction motors and the direct current traction generators of the time. In appearance the locomotive was similar to a late version GP9 or GP18 (i.e., often with a low short hood, but with the two exhaust stacks over the engine replaced by a single stack forward over the exit of the turbocharger, in common with later turbocharged EMD locomotives. An identification detail of the GP20 is the small radiator fan added ahead of the large aft fan.

De-turbo-ed GP20s, which employ 645 power assemblies, with Roots blowers replacing the EMD turbocharger without de-rating the horsepower of the locomotive, are somewhat common. As the reliability of the EMD turbocharger significantly improved over time, these de-turbo-ed examples became less common.

Original buyers

Railroad: Electro Motive Division (demonstrators)
Quantity: 4
Road numbers: 5625–5628
Notes: to Southern Pacific 7234–7237.

Railroad: Atchison, Topeka and Santa Fe Railway
Quantity: 75
Road numbers: 1100–1174

Railroad: Chicago, Burlington and Quincy Railroad
Quantity: 36
Road numbers: 900–935
Notes: to Burlington Northern Railroad 2036–2071.

Railroad: Great Northern Railway
Quantity: 36
Road numbers: 2000–2035
Notes: High short hood; to Burlington Northern Railroad 2000–2035.

Railroad: New York Central Railroad
Quantity: 15
Road numbers: 6100–6114
Notes: no dynamic brake; to Penn Central 2100-2114; to Conrail same numbers.

Railroad: Southern Pacific Company
Quantity: 34
Road numbers: 7200–7233

Railroad: St. Louis Southwestern Railway
Quantity: 20
Road numbers: 800–819

Railroad: Union Pacific Railroad
Quantity: 30
Road numbers: 700–729

Railroad: Western Pacific Railroad
Quantity: 10
Road numbers: 2001–2010
Notes: High short hood; Second Order used Blomberg B trucks from traded-in FTs.

Total Units: 260

Current owners
Current owners of GP20s include the Toledo, Peoria and Western Railway (TP&W) and the East Penn Railroad (ESPN). The ESPN's GP20s numbered 2062, 2064 and 2066 came from the Toledo, Peoria and Western Railway and are ex Santa Fe units, which then went to the New York, Susquehanna and Western Railway (NYSW) until they were sold to the ESPN in 2010. Watco companies operates three GP20s Nos. 2001-2003. The Alabama & Tennessee River Railroad (ATN) recently acquired GWR 5625. This unit is a former EMD Demonstrator of the same number. Blacklands operates GP20 No. 2036 which was originally AT&SF No.1152. The Georgia Northeastern operates GP20s Nos. 316 and 4125. Those units trace back to Great Northern No. 2016 and Southern Pacific No. 7205. The Sierra Railroad (Sierra Northern Railway (SERA)) operates GP20s ex-AT&SF 1162/3062 and ex AT&SF 1130/3030 (Currently as No. 48 and No. 50), as well as RJ Corman Railroad GP20 No. 4121.

Blue Ridge Scenic 4125 was originally Southern Pacific 7207 and is on the Blue Ridge Scenic RR.
Western Pacific 2001, the very first GP20 built, is preserved at Western Pacific Railroad Museum at Portola, CA.
VLIX 2003, originally Cotton Belt 815 is on loan to the Arkansas Railroad Museum in Pine Bluff, AR.

EMD GP20 Overview
Type and origin
Power type: Diesel-electric
Builder: General Motors Electro-Motive Division (EMD)
Model: GP20
Build date: November 1959 to April 1962
Total produced: 260
​ • AAR B-B
Gauge: 4 ft 8 1⁄2 in (1,435 mm)
Prime mover: EMD 567D2
Engine type: V16 diesel
Aspiration: Turbocharged
Cylinders: 16
Performance figures
Power output: 2,000 hp (1.5 MW)
Locale: United States

See also:

GM EMD Locomotives


Diesel-Electric Locomotives


Santa Fe Railroad 3055, an 1961 built EMD GP20, awaits its next duties in the yard at San Bernardino, December, 1987.  Photo by Sean Lamb.

By Slambo at en.wikipedia - Transferred from en.wikipedia(Original text : Photo by Sean Lamb (en:User:Slambo), CC BY-SA 2.0,

Santa Fe Railroad 3055, an 1961 built EMD GP20, awaits its next duties in the yard at San Bernardino, December, 1987. Photo by Sean Lamb.
WP No. 2001, the first production GP20, leads a special train in 2009. Note the high nose.
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